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Genetic modulators of fetal hemoglobin expression and ischemic stroke occurrence in African descendant children with sickle cell anemia.

  • Nicolau, Marta1
  • Vargas, Sofia1
  • Silva, Marisa1
  • Coelho, Andreia1
  • Ferreira, Emanuel1
  • Mendonça, Joana1
  • Vieira, Luís1, 2
  • Kjöllerström, Paula3
  • Maia, Raquel3
  • Silva, Rita4
  • Dias, Alexandra5
  • Ferreira, Teresa5
  • Morais, Anabela6
  • Soares, Isabel Mota7
  • Lavinha, João1, 8
  • Faustino, Paula9, 10, 11
  • 1 Departamento de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisbon, Portugal. , (Portugal)
  • 2 ToxOmics, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisbon, Portugal. , (Portugal)
  • 3 Unidade de Hematologia, Hospital de Dona Estefânia, Centro Hospitalar Universitário de Lisboa Central (CHULC), Lisbon, Portugal. , (Portugal)
  • 4 Unidade de Neuropediatria, Hospital de Dona Estefânia, CHULC, Lisbon, Portugal. , (Portugal)
  • 5 Núcleo de Hematologia, Departamento de Pediatria, Hospital Prof. Doutor Fernando Fonseca, Amadora, Portugal. , (Portugal)
  • 6 Departamento de Pediatria, Hospital de Santa Maria, Centro Hospitalar Universitário de Lisboa Norte, Lisbon, Portugal. , (Portugal)
  • 7 Departamento de Pediatria, Hospital Garcia de Orta, Almada, Portugal. , (Portugal)
  • 8 BioISI, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal. , (Portugal)
  • 9 Departamento de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisbon, Portugal. [email protected] , (Portugal)
  • 10 Instituto de Saúde Ambiental (ISAMB), Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal. [email protected] , (Portugal)
  • 11 Unidade de Investigação e Desenvolvimento, Departamento de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Avenida Padre Cruz, 1649-016, Lisbon, Portugal. [email protected] , (Portugal)
Published Article
Annals of Hematology
Publication Date
Dec 01, 2019
DOI: 10.1007/s00277-019-03783-y
PMID: 31478061


Sickle cell anemia (SCA) is an autosomal recessive monogenic disease with significant clinical variability. Cerebrovascular disease, particularly ischemic stroke, is one of the most severe complications of SCA in children. This study aimed to investigate the influence of genetic variants on the levels of fetal hemoglobin (Hb F) and biochemical parameters related with chronic hemolysis, as well as on ischemic stroke risk, in ninety-one unrelated SCA patients, children of sub-Saharan progenitors. Our results show that a higher Hb F level has an inverse relationship with the occurrence of stroke, since the group of patients who suffered stroke presents a significantly lower mean Hb F level (5.34 ± 4.57% versus 9.36 ± 6.48%; p = 0.024). Furthermore, the co-inheritance of alpha-thalassemia improves the chronic hemolytic pattern, evidenced by a decreased reticulocyte count (8.61 ± 3.58% versus 12.85 ± 4.71%; p < 0.001). In addition, our findings have confirmed the importance of HBG2 and BCL11A loci in the regulation of Hb F expression in sub-Saharan African SCA patients, as rs7482144_A, rs11886868_C, and rs4671393_A alleles are significantly associated with a considerable increase in Hb F levels (p = 0.019, p = 0.026, and p = 0.028, respectively). Concerning KLF1, twelve different variants were identified, two of them novel. Seventy-three patients (80.2%) presented at least one variant in this gene. However, no correlation was observed between the presence of these variants and Hb F level, severity of hemolysis, or stroke occurrence, which is consistent with their in silico-predicted minor functional consequences. Thus, we conclude that the prevalence of functional KLF1 variants in a sub-Saharan African background does not seem to be relevant to SCA clinical modulation.

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